1. Field of the Invention
The present invention relates to a recording and reading method and device of magneto-optical memory elements by means of a light-intensity modulated overwriting method.
2. Description of the Related Art
A normal recording and reading device of magneto-optical memory elements, as disclosed in the Japanese Patent Application Laying Open (KOKAI) No. 62-175948 and SPIE Vol. 1078 Optical Data Storage Topical Meeting (1989) pp 258-264, is designed so that a light-intensity modulated overwriting can be carried out on the magneto-optical memory elements containing a magnetic multi-layer film. The normal recording and reading device of the magneto-optical memory elements includes an optical head containing an objective lens and a laser source for irradiating a laser beam to the magneto-optical memory elements and modulating the intensity of the laser beam to high or low level, means for applying a recording magnetic field to the magneto-optical memory elements, and means for applying an initializing magnetic field to the magneto-optical memory elements.
If no cover, such as a cartridge case, is applied to the magneto-optical memory elements (for example, a compact disc), the light-intensity modulated overwriting can be carried out by the foregoing recording and reading device. In addition, the initializing magnetic field is applied to the magneto-optical memory elements at all the times or alternatively only during a recording. If, however, a cover such as a cartridge case is applied to the magneto-optical memory elements (for example, a floppy disk), it is difficult to obtain space which is wide enough to install both the means for applying the recording magnetic field to the magneto-optical memory elements and the means for applying the initializing magnetic field to the magneto-optical memory elements, because two separate means are required for applying the magnetic fields to the magneto-optical memory elements, in the foregoing recording and reading device. Therefore, the light-intensity modulated overwriting cannot be carried out on the magneto-optical memory elements which are accommodated in a cartridge case.